I recently used OF Dave Winfield 1984 (A/C-; .994, 2.01) at 1B for 140 starts. He posted a .995 FA and 10.326 RF there. That was 14th in FA and 9th in RF out of 16 full-time 1B's in the league. His FA was similar to guys rated C or D at 1B, and RF was similar to guys rated D, but with a lot of variability.
On the same team, I used 2B Glenn Hubbard 1984 (A-/A; .988/5.80) at 3B for 54 starts. He posted a .982 FA and 3.378 RF at 3B. If he'd had enough IP to qualify for the leaderboard, that would have tied for first in FA and ranked 6th in RF (compared to 17 qualifiers). He was much better for me than Barry Bonnell (rated C/D- at 3B, but only 10 games there in real life) and somewhat comparable to Bob Horner (A-/C-, with 32 games at 3B in real life).
I also used 1981 2B Glenn Hubbard (A/B; .991/5.45) in 39 starts at 3B. That season he gave me a .944 FA and 2.939 RF, which would have ranked 19th and 21st in the league if he'd qualified for the leaderboard.
Hubbard's real-life defensive stats at 2B were pretty similar both of the seasons, but he performed much better for me at 3B in 1984 than 1981. Probably that is just a fluke of small sample size, with only ~40 starts per season.
I'm thinking about splitting Hubbard (A-/A+ at 2B) and Winfield (A-/C+ in OF) at 3B there for 1985, but am worried about any OF making a ton of errors at 3B.